Among variable valve mechanisms, there is a variable valve mechanism 109 according to a related art as shown in FIG. 10 to FIG. 11B. The variable valve mechanism 109 includes: an input arm 130; an output arm 140; three switching pins 151, 152 and 153; and a displacing device 159. The input arm 130 rocks as the input arm 130 is pressed by a cam 110. The output arm 140 rocks to actuate a valve 7. The switching pins 151, 152 and 153 are inserted through the input arm 130 and the output arm 140, and are provided so as to be displaceable between a coupling position P and a non-coupling position Q. In the coupling position P, the switching pins 151, 152 and 153 extend across the input arm 130 and the output arm 140. In the non-coupling position Q, the switching pins 151, 152 and 153 do not extend across the input arm 130 and the output arm 140. The displacing device 159 displaces the switching pins 151, 152 and 153.
The displacing device 159 includes: a pressing device 160; a return spring 170; a left stopper mechanism 182; and a right stopper mechanism 183. The pressing device 160 presses the three switching pins 151, 152 and 153 from the right-side coupling position P to the left-side non-coupling position Q. The return spring 170 presses the three switching pins 151, 152 and 153 back from the left-side non-coupling position Q to the right-side coupling position P. The left stopper mechanism 182 stops a displacement of the three switching pins 151, 152 and 153 at the non-coupling position Q. The right stopper mechanism 183 stops the three switching pins 151, 152 and 153 at the coupling position P.
The return spring 170 is interposed between the left end face of the left-end switching pin 151 and the bottom portion of a pin hole in which the left-end switching pin 151 is inserted, and presses the left end face of the left-end switching pin 151 rightward with its restoring force.
The left stopper mechanism 182 is formed of the bottom portion of the pin hole in which the left-end switching pin 151 is inserted. The right stopper mechanism 183 is formed of a ring-shaped protrusion that protrudes inward at a right opening of a pin hole in which the right-end switching pin 153 is inserted.